The present invention relates to shotgun chokes. More particularly, the present invention relates to an easily installed shotgun choke for providing a pattern of shot ideal for situations involving use of a shotgun against personnel at short range.
A shotgun choke is a device well known in the art. It has been known to vary the shape and length of the barrel of the shotgun, particularly the end of the barrel, to alter the projectile path of the shot pellets after leaving the barrel of the gun. After leaving the confines of the shotgun barrel, the kinetic energy of the mass of pellets is no longer constrained from expanding in diameter, thus providing an alternative direction in which to travel besides moving forward. The kinetic energy of the mass of pellets, and ricochets from individual pellets hitting each other, will cause the mass of pellets to spread out into a larger diameter the farther it travels from the barrel within the range of the gun. Shotgun chokes are used to control the rate at which these pellets spread out and also to control the manner or "pattern" in which the pellets spread out after leaving the gun barrel. The natural pattern of this spread is circular, although it is known to use the choke to modify the shape of the pattern from a circular pattern to some other pattern to accomplish a particular purpose. For example, the device disclosed by Fleming (U.S. Pat. No. 2,167,173) discloses a shotgun barrel which contains a flared portion on a particular side of the barrel near the end. The barrel end is flared to create a bias in the pattern of shot so that a lopsided pattern is produced. The lopsidedness of the pattern is intended to compensate for a hunter which has a consistent habit of shooting above, behind, below, or above his or her target. For example, if the hunter tends to shoot under the target too often, a flare will be placed along the top of the barrel end to scatter some of the shot above the periphery of the normal circular pattern. Fleming also discloses a device with flares at both sides of the barrel end, supposedly to obtain a wider pattern. However, a mass of pellets travelling through a shotgun barrel has a fixed amount of potential kinetic energy. In order to obtain the widest possible pattern in the shortest possible distance, it is necessary to transfer some of the kinetic energy expended in dispersing the pattern vertically to the energy used to disperse the pattern horizontally. In other words, if the vertical spread of the pattern can be restricted, this will transfer energy to the horizontal forces in the pellets and increase the horizontal spread. Fleming does not vertically restrict the pellet's path, with the result being that the width of the pattern is not as wide as is capable of being achieved.
In the anti-personnel field, the user of a shotgun is generally not concerned with obtaining the maximum effective range available from the particular gauge of shotgun as in hunting situations, but, will instead be more concerned with achieving a particular pattern. For instance, a wide pattern (larger horizontally than vertically) is often desirable in situations of armed conflict, such as guerrilla warfare or a SWAT team. Because confrontations in these situations often occur at very close range, quick reactions on the part of the user of the shotgun are at a premium. There is seldom sufficient time for the user to take careful aim at a target, and he or she will only have time to fire the weapon in the general direction of the target. Thus, a pattern which covers a wide area is needed. At the same time, the effective range of the shotgun is generally not an important criteria. If the weapon is being fired by a member of a SWAT team inside of a building, the room in which the weapon is fired will generally not be more than twenty-five to forty feet long. For this reason, it is desirable that the shot pattern be able to spread as wide as possible within a twenty-five to forty foot range. In any case, the maximum effective range necessary is generally no greater than twenty-five yards.
A design limitation for shotgun chokes is that they should be capable of withstanding extremely high pressures and temperatures without significant metal fatigue. Even the slightest metal fatigue is intolerable, because chokes are expected to have a useful life equally as long as the weapon upon which they are used.
A further desirable feature of chokes is to provide a choke which can be easily attached to existing shotguns. Many shotgun chokes are designed as an integral a part of the barrel, so that the barrels must be switched out when a change in choke is desired. It is much less expensive to provide a choke which attaches to the end of the barrel of any common shotgun than to machine a choke as part of the barrel which would require the manufacture of separate barrels.
A number of shot pattern modification devices exist in the prior art. However, it is believed that they contain unsuitable limitations for use as an anti-personnel shotgun choke. The limitations of Fleming (U.S. Pat. No. 2,167,173) have already been discussed. The Applicant is a co-inventor of two related patents (U.S. Pat. Nos. 3,676,947 and 3,492,750). These devices contain a primary feature of vents to "divert" gases which are driving the shotgun pellets. While the devices disclosed are capable of throwing a relatively wide pattern, testing of the devices by the Applicant and a branch of the United States armed forces has revealed that with a twenty inch barrel and #4 buckshot, the devices will throw a pattern approximately 143/4 inches high and 351/2 inches wide at 32.70 feet. As will be described later, Applicant's invention offers a much wider pattern at a similar distance. The device disclosed in Sargeant et al. (U.S. Pat. No. 3,226,871) shows a shotgun choke known as the "duck bill" choke. While this duck bill choke is capable of throwing a relatively wide pattern, it may suffer from important and unnecessary structural weakness from the notches formed in the barrel. Particularly in the duck bill design, the heat and force of a shotgun blast can cause the top or bottom or both portions of the device to crack and fly off. The device disclosed by Wilhelm et al. (U.S. Pat. No. 3, 729,848) is a hand gun for discharging specially designed shot-type ammunition which contains a wide, narrow flange for providing a linear shot pattern. Although the device claims to provide a linear shot pattern, hand guns are inappropriate for using most standard gauges of shot, such as 12 gauge, 16 gauge and 20 gauge, although a few shotgun pistols are known to exist. These shotgun pistols are, to the Applicant's knowledge, usually found in smaller gauges, such as 410 gauge and less. The large kickback of a large gauge charge makes the pistols difficult to fire, and the small size of the pistol severely limits the number of shells which may be held in the magazine. This latter limitation is a severe limitation for anti-personnel use, as the magazine should be capable of holding a large number of shells to provide an adequate safety factor. Also, the device must be specially made and cannot be adapted to existing shotguns. Other devices for altering shot patterns are found in Lowry (U.S. Pat. No. 3,496,667), Cutts (U.S. Pat. No. 2,098,617) and Devol (U.S. Pat. No. 966,889). All of these devices alter the pattern of shot, but do so in a circular fashion, so that the vertical kinetic energy of the shot is not efficiently transferred into horizontal kinetic energy, making the width of the pattern inadequate.
Therefore, it is an object of the present invention to provide a shot pattern modification device for shotguns, otherwise known as a choke. It is an object of the present invention to provide a shotgun choke which has an extremely wide shot pattern for use as an anti-personnel weapon but which has an effective range sufficient to reach through most rooms and hallways in buildings. It is a further object of the present invention to provide a durable and safe shotgun choke. It is a further object of the present invention to provide a shotgun choke which is easily installed on most standard models of shotguns. Other objects of the invention will become evident when the invention is described hereafter.